2. Just half an ounce of plastic made this crater in a block of aluminum.

3. In 2012, surgeons implanted the first 3D-printed titanium lower jaw in an 83-year-old woman.

And she was home from the hospital just four days later. "The surgery time decreases because the implants perfectly fit the patients and hospitalization time also lowers — all reducing medical costs," one of the doctors said.

6. Another Lichtenberg figure, this time all over the ground, was caused by a downed power line.

7. You don't see transparent fish every day — maybe because they're transparent.

Sea salps are completely docile and don't sting or bite. But it's rare to find them alone — they typically travel in large groups that have been known to clog up intake pipes and even shut down a nuclear plant.

21. Kondyor Massif in Eastern Russia looks like an impact crater or a volcano, but it's not.

It's called an "intrusion" in geology, formed when magma crystallizes below the surface. It's five miles in diameter, the site of a huge platinum mine, and is also the source of its own mineral, called Konderite.

22. If you need further evidence against sharing needles, here's proof that a needle might not be as clean as it looks.

Tails down, noses up, they're known to catch quick naps of 10-15 minutes just like this. In captivity, whales have been observed sleeping with one half of their brain at a time, while the other half does things like swimming, breathing, and communicating.